Is it normal..that i'm more sexually attracted to bf when he's fatter?

I suppose I have a bit of a fat fetish or am a chubby chaser... I did not realize this until getting with my boyfriend, who I lost my virginity to. I'm 21, he's about to be 23. He's about 5ft 9, I'm 5ft 6. Everything was great when I met him a year ago. We had sex about 3 months in. Due to work, stress, sleep, etc, he started to gain weight. He went from about 170 to 187. I realized.. I liked it. The weight stayed mostly in his stomach area, a little in the butt. And I loved it, loved when he over ate and looked even fatter. I loved having sex, especially with him on top. I loved feeling him shirtless against me. But lately he's lost most of the weight, and is getting more toned..and sex is suffering. I haven't told him any of this, because, let's face it, the chubby fetish thing is pretty darn weird. But it now makes it hard for me to have sex or enjoy it, and I think he's worried it's his fault but he doesn't know what's wrong. And he's happier this way, than he was with the stomach. I love him, and there's no way I'd leave him. And I'm okay without sex..but I know he wants it and hates that I don't feel the same anymore. Should I just...fake it? :(